And was the code you've shown for the association the code created by
the LINQ to SQL designer, or was it hand-written?

The model I've got in my test app has a lot more code for the setter...
however, it all works. For example, in my test defect database, I've
got:

           using (var context = new DefectModelDataContext())
           {
               context.Log = Console.Out;

               Console.WriteLine("Loading defect");
               var defect = (from bug in context.Defects
                            where bug.Summary.Contains("Welsh")
                            select bug).Single();

               Console.WriteLine("Using Project property...");
               Console.WriteLine("Project={0}", defect.Project.Name);
           }

The output is:

Loading defect
SELECT [t0].[DefectID] AS [ID], [t0].[Created], [t0].[LastModified],
[t0].[Summary], [t0].[Severity], [t0].[Status], [t0].
[AssignedToUserID], [t0].[CreatedByUserID], [t0].[ProjectID]
FROM [dbo].[Defect] AS [t0]
WHERE [t0].[Summary] LIKE @p0
-- @p0: Input NVarChar (Size = 7; Prec = 0; Scale = 0) [%Welsh%]
-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build:
3.5.21022.8

Using Project property...
SELECT [t0].[ProjectID], [t0].[Name]
FROM [dbo].[Project] AS [t0]
WHERE [t0].[ProjectID] = @p0
-- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [1]
-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build:
3.5.21022.8

Project=Skeety Media Player